#! /usr/bin/env python3
#
def problem0 ( ):

#*****************************************************************************80
#
## problem0(): Examine file 'five_letters.txt'.
#
  print ( '' )
  print ( 'problem0():' )
  print ( '  How many words are in the list?' )
  print ( '  Does the list contain "osier"?' )
  print ( '  What is the 100th word in the list?' )
  print ( '' )

  filename = 'five_letters.txt'
  words = []
  input = open ( filename, 'r' )
  for line in input:
    words.append ( line.strip() )

  print ( '  The file ' + filename + ' contains ', len ( words ), ' words.' )
  print ( '  Is "osier" in the file:', ( 'osier' in words ) )
  print ( '  Word 100 = "' + words[99] + '" or "' + words[100] + '"' )

  return

def problem1 ( ):

#*****************************************************************************80
#
## problem1(): Find words containing 'rat'
#  
  print ( '' )
  print ( 'problem1():' )
  print ( '  Which words contain "rat"?' )
  print ( '' )

  filename = 'five_letters.txt'
  words = []
  input = open ( filename, 'r' )
  for line in input:
    words.append ( line.strip() )

  for word in words:
    if ( 'rat' in word ):
      print ( word )

  return
  
def problem2 ( ):

#*****************************************************************************80
#
## problem2(): Matrix-vector multiplication.
#
  from magic_matrix import magic_list
  
  print ( '' )
  print ( 'problem2():' )
  print ( '  Compute A*x for magic matrix.' )
  print ( '' )

  n = 5
  A = magic_list ( n )
  x = [ 1, 1, 1, 1, 1 ]
  rowsum = [ 0, 0, 0, 0, 0 ]
  for i in range ( 0, n ):
    for j in range ( 0, n ):
      rowsum[i] = rowsum[i] + A[i][j] * x[j]

  print ( '  rowsums:', rowsum )
  return

def problem3 ( ):

#*****************************************************************************80
#
## problem3(): Matrix diagonal and antidiagonal sums.
#
  from magic_matrix import magic_list
  
  print ( '' )
  print ( 'problem2():' )
  print ( '  Compute A*x for magic matrix.' )
  print ( '' )

  n = 7
  A = magic_list ( n )

  dsum = 0
  for i in range ( 0, n ):
    dsum = dsum + A[i][i]
  print ( '  diagonal sum:', dsum )

  asum = 0
  for i in range ( 0, n ):
    asum = asum + A[i][n-1-i]
  print ( '  antidiagonal sum:', asum )

  return
  
def problem4 ( ):

#*****************************************************************************80
#
## problem4(): Find palindromes
#  
  print ( '' )
  print ( 'problem4():' )
  print ( '  Find palindromes.' )
  print ( '' )

  filename = 'five_letters.txt'
  words = []
  input = open ( filename, 'r' )
  for line in input:
    words.append ( line.strip() )

  for word in words:
    if ( word[::-1] in words ):
      print ( word )

  return

def problem5 ( ):

#*****************************************************************************80
#
## problem5(): Monte Carlo estimate of pi.
#
  from random import random
  from math import pi

  print ( '' )
  print ( 'problem5():' )
  print ( '  Estimate pi using the Monte Carlo method' )
  print ( '' )

  n = 100
  k = 0
  for i in range ( 0, n ):
    x = random ( )
    y = random ( )
    if ( x**2 + y**2 <= 1.0 ):
      k = k + 1

  pi_est = 4 * k / n
  pi_err = abs ( pi - pi_est )

  print ( '  Number of samples n = ', n )
  print ( '  Estimate for pi is ', pi_est )
  print ( '  Exact value is     ', pi )
  print ( '  Error is           ', pi_err )

  return
 
def problem6 ( ):

#*****************************************************************************80
#
## problem6(): Convert DNA string to list of codons.
#  
  print ( '' )
  print ( 'problem6():' )
  print ( '  Convert DNA string to codon list.' )

  dna = 'AGTCTTATATCT'
  print ( '  The DNA string: ' + dna )

  for frame in [ 0, 1, 2 ]:
    codon_list = dna_to_codon_list ( dna, frame )
    print ( codon_list )

  return

def dna_to_codon_list ( dna, frame ):

  codon_list = []

  n = len ( dna )
  pos = frame

  while ( pos + 3 <= n ):
    codon_list.append ( dna[pos:pos+3] )
    pos = pos + 3

  return codon_list
  
def problem7 ( ):

#*****************************************************************************80
#
## problem7(): find anagrams.
#  
  print ( '' )
  print ( 'problem7():' )
  print ( '  Find anagrams of a five letter word' )
  print ( '' )

  filename = 'five_letters.txt'
  words = []
  input = open ( filename, 'r' )
  for line in input:
    words.append ( line.strip() )

  target = 'parts'
  print ( '  Looking for anagrams of "' + target + '"' )
  print ( '' )
  
  for word in words:
    if ( sorted ( word ) == sorted ( target ) ):
      print ( word )
 
  return
  
def problem8 ( ):

#*****************************************************************************80
#
## problem8(): scalar product and cross product.
#  
  print ( '' )
  print ( 'problem8():' )
  print ( '  Given 3-dimensional vectors v1 and v2.' )
  print ( '  compute v1 dot v2 (a number) and v1 cross v2 (a vector).' )
  print ( '  Use lists to represent vectors.' )
  print ( '' )

  n = 3

  a = [ 1, 2, 3 ]
  b = [ 4, 5, 6 ]

  dot = 0
  for i in range ( 0, n ):
    dot = dot + a[i] * b[i]

  print ( '  dot product = ', dot )

  cross = [ 0, 0, 0 ]
  cross[0] = a[1] * b[2] - a[2] - b[1]
  cross[1] = a[2] * b[0] - a[0] - b[2]
  cross[2] = a[0] * b[1] - a[1] - b[0]

  print ( '  cross product = ', cross )

  return

def problem9 ( ):

#*****************************************************************************80
#
## problem9(): p[i] is product of all a[] except i-th entry.
#
  print ( '' )
  print ( 'problem9():' )
  print ( '  p[i] = product of all but i-th entry of a.' )
  print ( '' )

  a = [ 1, 2, 3 ]
  print ( '  a:', a )

  n = len ( a )
  p = []
  for i in range ( 0, n ):
    p.append ( 1 )

  for i in range ( 0, n ):
    for j in range ( 0, n ):
      if ( j != i ):
        p[i] = p[i] * a[j]

  print ( '  p:', p )

  return

if ( __name__ == "__main__" ):
  problem0 ( )
  problem1 ( )
  problem2 ( )
  problem3 ( )
  problem4 ( )
  problem5 ( )
  problem6 ( )
  problem7 ( )
  problem8 ( )
  problem9 ( )